From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-dy1-f180.google.com (mail-dy1-f180.google.com [74.125.82.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0CF6536A378 for ; Tue, 12 May 2026 18:10:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.82.180 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778609432; cv=none; b=Y+chlasOCyfjWPDHa92IcRIPccAuzNl1Pz8YQ6NnKfmoMGt27TMQ0skZXmChC2E8TFUFNyy6shGJAjrpX0VjOy3QwKEXGKWOSK7OIVvxe/RqJiVnhgyiBq+Z4U/+xshEEFhKO2mb5pvE7MdfAem+X2V+0OR9C7ZKws8abCOBWYo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778609432; c=relaxed/simple; bh=fX4OvBVV8Pd7ppnT5E3rnJzlKJlg/3XrfBXMkyWB0oY=; h=Message-Id:In-Reply-To:References:From:Date:Subject:Content-Type: MIME-Version:To:Cc; b=ic0w0dzSmF3NBzTd3kzvTKVDyLfRpSp2wg6Uyf5vvMMk4J37fKpGUtibdX3HNN0pe+PbObZ9WHJnTvB/+TS7Yv8Z/4T+ZR9mPSRNf31AXjffLWGc+1W5ei8gYe5Ln+u+R5FCHLDPJrFCwyVmaXVSUW0bIWtP3q9sEO98k9XMDmo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=Z3wve2q/; arc=none smtp.client-ip=74.125.82.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Z3wve2q/" Received: by mail-dy1-f180.google.com with SMTP id 5a478bee46e88-2f7ca62a3c4so6088323eec.0 for ; Tue, 12 May 2026 11:10:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1778609430; x=1779214230; darn=vger.kernel.org; h=cc:to:mime-version:content-transfer-encoding:fcc:subject:date:from :references:in-reply-to:message-id:from:to:cc:subject:date :message-id:reply-to; bh=vcLsdeWMhUMQPfZNq5JY+8B03eHo1E5r5hp/TD9BEIk=; b=Z3wve2q/tifJBot2LCOh8ZzkxEcYRQ0FDbNhvA8xGw2e8f7yDWGe2bdDvbahlqhxpH xPE3pO+yZWDLPth8sCXD+0HFRFceqcZqe5SViSb0TJijuX49Fv/X/om5UOrB8iVU/y7V zR6zbJ0wnKG9GVGvd/CqK+aArFI+hWqf/v2vjQ7ODPTLvcBkl1OskHs9ZzZIdBHV7atN i5YtcCTSZyc7gWQ8ZaeGWLjTQ1rMbQfmWqhsbzBsTKhTpalHTG0ufH9D0+s8d1qw6cxS PnpC5t24pjEl0E7T3g1QEiILpMCj49OGNY2xAkfGCpCi/9fHiBwmJ+tfmxgFcG33/rXL QOyg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778609430; x=1779214230; h=cc:to:mime-version:content-transfer-encoding:fcc:subject:date:from :references:in-reply-to:message-id:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=vcLsdeWMhUMQPfZNq5JY+8B03eHo1E5r5hp/TD9BEIk=; b=jq+znNE41hc9lrig7JOx5YM8ajpPAuiTSHazfoyzZAVCe/4dUNQSlASOamapD/OWn4 c6ZQurhHzFbLd7MQl/YuOvaYKpcHZwaUxCO6WfSJ3woSdAbri4nwfXiSqkalYGTGRV+F XpMO7COGAQpeDaxRulnwu8AwI1LjFlGnmHcSYaosEO2BBbL/zKIrWZlo9gX83jveix6C LZUdXbj6e2vE5DI63RIfNq632zmkqtHnjH8gjWyPIiu4r1fSopDqlTKylKaRIcGtin+F nUDdgS2usLKXlvok1lVjH11o5uwLu3wLuTcyzhAzjvr13B2AP3bjAQDL9nCZ3Xr5QUrc 8hRQ== X-Gm-Message-State: AOJu0YybqxA6IHPnO2H+SuGrRhRzvV+02xEtW4TR+JAaJm3iuzgP/1Hf vGBNXpVSkDL6uSIe+c0JNidrKIR7+Hjd7KEi8M3/eKhV9XYW4erRWIaCOTM9Ng== X-Gm-Gg: Acq92OGLPCjPOlE8yo8ohbE+Tra6VPPdXcoMt5mU9KCOWdrgBbGvA0G5pWqUWOgYoGw 0SQQAWnnOEszyk0b7quqp1oJhNwZ5NEbjxKFwVz8zFvCjA4zWwNcdHqmtGJYyocE8fvrjYGMz6e ekGawtRysCkI/gcBAsI3NsuhtfAUt6DjFwwXcpJ6us8Al5Whccwb3Is2TsRwTjpZUBzNZeyfr3O G+yvq9jzQoU5l1mtAUrkfrlZ77DRiV3In6JxI9sgCyJlCXTuHm2hbhPPshIoVD0cGzIzTB2j+lq KnIkBxC30ToYR0y331CKdDL/Rtlkx4p54OfbRs3uyjTum928Jf3EVBPz5G/JpzFw529rzV2ShOA xEpI02CIJCrDg+cWdkgp1Vpf6aPD9SZF/Ijpk3G3Mn5oFKbwtGICC9+O31mgdWOz5awES0WW2zD VhOPe3OdKVd87ybSgIn7yjv8eD1k0= X-Received: by 2002:a05:7301:290e:b0:2d8:71c2:255d with SMTP id 5a478bee46e88-30118ca4b2bmr119445eec.14.1778609429684; Tue, 12 May 2026 11:10:29 -0700 (PDT) Received: from [127.0.0.1] ([57.151.128.208]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2f88885b87dsm22854073eec.21.2026.05.12.11.10.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 May 2026 11:10:29 -0700 (PDT) Message-Id: <020ca774c0ec3abadb5c987c93373f11d67d5880.1778609423.git.gitgitgadget@gmail.com> In-Reply-To: References: From: "Michael Montalbo via GitGitGadget" Date: Tue, 12 May 2026 18:10:22 +0000 Subject: [PATCH v2 3/4] xdiff: guard against negative context lengths Fcc: Sent Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 To: git@vger.kernel.org Cc: Michael Montalbo , Michael Montalbo From: Michael Montalbo The xdemitconf_t fields ctxlen and interhunkctxlen are typed as long (signed), but negative values are not meaningful for context line counts. Unlike the diff_options fields changed in the previous two commits, these cannot be converted to unsigned because the xdiff arithmetic relies on signed subtraction: s1 = XDL_MAX(xch->i1 - xecfg->ctxlen, 0); If ctxlen were unsigned long, the signed operand would be implicitly converted to unsigned, and the subtraction would wrap to a large positive value when i1 < ctxlen, defeating the XDL_MAX clamp. The signed type is required for correct context-window calculations. The previous two commits reject negative values at the parse layer for --inter-hunk-context and -U/--unified, so negative values should no longer reach xdiff in normal use. Add BUG() guards at the top of xdl_get_hunk() as defense in depth to catch programming errors in current or future callers that bypass option parsing. xdl_get_hunk() is called by both xdl_emit_diff() and xdl_call_hunk_func(), so a single guard covers all xdiff consumers. Signed-off-by: Michael Montalbo --- xdiff/xemit.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/xdiff/xemit.c b/xdiff/xemit.c index 04f7e9193b..7cd9cf0a44 100644 --- a/xdiff/xemit.c +++ b/xdiff/xemit.c @@ -46,12 +46,20 @@ static long saturating_add(long a, long b) xdchange_t *xdl_get_hunk(xdchange_t **xscr, xdemitconf_t const *xecfg) { xdchange_t *xch, *xchp, *lxch; - long max_common = saturating_add(saturating_add(xecfg->ctxlen, - xecfg->ctxlen), - xecfg->interhunkctxlen); - long max_ignorable = xecfg->ctxlen; + long max_common; + long max_ignorable; long ignored = 0; /* number of ignored blank lines */ + if (xecfg->ctxlen < 0) + BUG("negative context length: %ld", xecfg->ctxlen); + if (xecfg->interhunkctxlen < 0) + BUG("negative inter-hunk context length: %ld", xecfg->interhunkctxlen); + + max_common = saturating_add(saturating_add(xecfg->ctxlen, + xecfg->ctxlen), + xecfg->interhunkctxlen); + max_ignorable = xecfg->ctxlen; + /* remove ignorable changes that are too far before other changes */ for (xchp = *xscr; xchp && xchp->ignore; xchp = xchp->next) { xch = xchp->next; -- gitgitgadget